Phytoneuron

: Eupatorieae) — acceptance of its specific status.

OXYLOBUS SUBGLABER KING & H. ROB. (ASTERACEAE: EUPATORIEAE) -
ACCEPTANCE OF ITS SPECIFIC STATUS

Billie L. Turner
Plant Resources Center

The University of Texas
Austin TX 78712

ABSTRACT

Oxylobus subglaber, treated as a synonym of O. arbutifolius by Turner and Kerr (1985) in
their revision of the genus, is resurrected to specific rank this a result of additional specimens
collected from the general region of the type locality. Oxylobus was previously treated as having but
4 species; the present reestablishment and the previous description of the novelty O. preecei by
Turner (1988) now brings the total to 6 species. A key to the taxa is provided, along with a map
showing the distribution of the revised set of accepted species.
KEY WORDS: Asteraceae, Eupatorieae, Oxylobus, Mexico

Oxylobus (Moc. ex DC.) A Gray is a genus positioned in the subtribe Oxylobinae of the
Eupatorieae, along with eight other genera, most notably Ageratina Spach (Hind & Robinson 2009).
The present reassessment of the group was occasioned by the resurrection of O. subglaber and the
need to account for the recently described O. preecei. So constructed, the genus now contains six
well marked species, as follows.

1. Flowering stems with mostly 2-5 pairs of basal leaves: perennial herbs

Oxylobus adscendeus (Sch. Rip. ex Hemsl.) B.L. Rob. & Greenm.

1. Flowering stems with mostly 10 or more pairs of leaves; suffratieose herbs or subshrubs.

2. Involucres 3-4 mm high; peduncles not markedly glandular pubescent.

3. Involucral bracts broadly rounded apically; pappus of achenes 0.2 mm long or less

Oxylobus subglaber King & H. Rob.

3. Involucral bracts acute apically; pappus of achenes 0.3-0.5 mm long
Oxylobus oaxacanus Blake

2. Involucres 4.3-7.0 mm high; peduncles markedly glandular pubescent.

4. Leaf blades mostly 2.2-6.0 cm long. 1-3 cm wide, densely pubescent
Oxylobus glandulifer (Sch. Bip. ex Hemsl.) A Gray ex Klatt

4. Leaf blades mostly 1-2 cm long, 0.5-1.2 cm wide, sparsely pubescent
to glabrous or nearly so.

5. Leaves to some extent glandular pubescent; heads not borne on elongate naked scapes

Oxylobus arbutifolius (Kunth) A Gray

5, Leaves glabrous; heads borne on elongate naked scapes .... Oxylobus preecei B.L. Turner

Turner and Kerr (1985) provided a detailed account of four of the above species; the two
species added to the genus since are enlarged upon below. Distribution of the two additional taxa are
shown in Fig. 3.

Turner: Oxylobus subglaber 2

OXYLOBUS PREECEI B.L. Turner, Phytologia 65: 375. 1988. Fig. 1. TYPE: MEXICO. Pueblo.
Mpio. Coxcatlan, W of Tepeloya, ca 22 km from Coxcatlan, ca 2560 m, 15 Apr 1985, P.
TenorioL. 8804 (holotype: TEX).

As can be noted in the sketch of the present novelty by Turner (1988), the habit of Oxylobus
preecei is very similar to O. subglaber. It differs from the latter in numerous characters, including
shape and size of the involucral bracts and characters of the pappus. Turner speculated that O.
preecei might have been derived from "ancestral hybridization" between O. arbutifolius and O.
oaxacanus, since it combines features of both taxa.

OXYLOBUS SUBGLABER King & H. Rob. [as Oxylobus 'subglabrus'], Phytologia 27: 385. 1973.
TYPE: MEXICO. Oaxaca. Distrito Ixtlan, Cerro de Humo Chico, 2 Sep 1966, T.

Macdougall 8 (holotype: US!).

Additional collections examined. MEXICO. Oaxaca. Distrito Ixtlan, Near Cerro Pelon,
59 km SW of Valle National ... on open cliff, 28 Sep 1994, Yahara & Soejima 118 (TEX); 32.9 km
N from Ixtlan along Mexico Hwy J 75 to Valle Nacional, 2780 m, "Road-cut in edge of dense pine
forest," 17° 30.3' N, 96° 30.4' W, 10 Nov 1997, Yahara et al. 1100 '(TEX).

Specimen observations along with label data on the two Yahara collections, "On open cliff,"
and along "Road-cut," suggest that the species is a bluff-dwelling species having a low, stoloniferous
habit.

Oxylobus subglaber, originally known by a single collection from north-central Oaxaca,
Mexico, was placed by Turner and Kerr (1985) in synonymy with the widespread and highly variable
O. arbutifolius (Kunth) A. Gray; they noted, however, that the plant concerned was an "unusual
form" of O. arbutifolius. Indeed, the senior author (BLT) subsequently studied the type in more
detail (cf Fig. 2), noting that its specific status might be "good." This has proved to be the case, to
judge from the additional collections assembled by Yahara et al.

Both of the more recent collections are very similar to the type of Oxylobus subglaber in
habit, foliage, and floral details. In my early assessment of the taxon, as noted above, I compared it
with O. arbutifolius, but it is clearly closer to O. oaxacanus Blake and the recently described, local
endemic O. preecei B.L. Turner from Pueblo. Both of the latter possess similar habits and
capitulescences, but O. preecei is readily distinguished from O. subglaber by having distinctive,
oblanceolate, leaves, longer, linear-lanceolate involucral bracts, and more pronounced pappus scales.

ACKNOWLEDGEMENTS

ACKNOWLEDGEMENTS
Thanks to US for a loan of type material of Oxylobus subglaber, to Tom Wendt for the
photograph of O. preecei, and to Guy Nesom for helpful suggestions on the manuscript. Distribution
maps are based upon specimens on file at LL-TEX.

LITERATURE CITED

Hind, D.J.N, and H.E. Robinson. 2007. Eupatorieae, in The Families and Genera of Vascular Plants

8: 510-575.
Turner, B.L. 1988. A new species of Oxylobus (Asteraceae: Eupatorieae) from Pueblo, Mexico.

Phytologia 65: 375.
Turner, B.L. and K.M. Kerr. 1985. Revision of the genus Oxylobus (Asteraceae-Eupatorieae). PI.

Syst. Evol. 151:73-87.

Turner: Oxylobus subglaber 3

Figure 1. Holotype of Oxylobus preecei (TEX).

Turner: Oxylobus subglaber 4

Figure 2. Sketches of Oxylobus subglaber (from holotype).

Turns: Qxytobus subgiabs 5

OXYLOBUS

Figure 3. Distribution of Oxylobus oacacanus, O.preecei, and O. subglaber — Puebla, Oaxaca, ana
Chiapas.